Over the past several decades the use of spark ignited two-stroke internal combustion engines has steadily increased. They are presently found in power lawn mowers and other power operated garden equipment, power chain saws, pumps, electrical generators, marine outboard engines, snowmobiles, motorcycles and the like.
The increasing use of two-stroke cycle engines, coupled with increasing severity of the conditions in which they have operated, has led to an increased demand for oils to adequately lubricate such engines. Among the problems associated with two-stroke cycle engines is piston lubricity, scuffing or scoring. This condition is generally controlled by adding relatively high viscosity oils (greater than or equal to 100 centistokes (cSt) at 40.degree. C.) or bright stock. The higher viscosity oils and bright stock act to increase viscosity and prevent piston seizure. A problem associated with the use of these materials is deposit or varnish formation in the combustion chamber, which may lead to preignition. High molecular weight polymers may be used to replace some or all of bright stock in two-stroke cycle engines. The polymer acts to increase viscosity and prevent piston seizure. The problem associated with the use of bright stock or high viscosity oils or high molecular weight polymers is that the products tend to cause fouling of the spark plug in a two-stroke cycle engine.
The unique problems and techniques associated with the lubrication of two-stroke cycle engines has led to the recognition by those skilled in the art of two-stroke cycle engine lubricants as a distinct lubricant type. See, for example, U.S. Pat. Nos. 3,085,975; 3,004,837; and 3,753,905.
The compositions of the present invention are effective in controlling piston scuffing and ring wear. These benefits are obtained without requiring the use need of high molecular weight polymers, bright stock or high viscosity oils.